1. Field of the Invention
The present invention relates to a maximum voltage detecting apparatus using ferroelectric capacitors and, more particularly, to an apparatus for detecting the maximum voltage output from an apparatus for generating a potential such as a light sensor, a heat sensor or a pressure sensor by using ferroelectric capacitors and without the need for an external power supply, and to a method of producing ferroelectric capacitors.
2. Description of the Related Art
A light sensor, a heat sensor, a pressure sensor, a wind force sensor or the like generates a potential which corresponds to the light, the heat, the pressure or the like to be measured. A comparator such as a comparator 10 shown in FIG. 1 is used as a monitor for judging whether or not the potential has reached a predetermined value. The comparator 10 is generally composed of a current mirror circuit 10a and a differentiating circuit 10b, and a voltage which corresponds to the difference between the output at the non-inverting input terminal and the output at the inverting input terminal is taken out as an output. An apparatus for generating a potential such as a light sensor or a heat sensor is connected to the non-inverting input terminal, and a reference voltage is applied to the inverting terminal so as to judge whether or not an external voltage such as the voltage of a light sensor or a heat sensor has reached the reference voltage.
A conventional voltage measuring apparatus such as a comparator, however, cannot be operated unless power is supplied from an external power source 10c. In addition, in order to constantly monitor the maximum voltage, it is also necessary to connect an external memory to the output terminal of the comparator, which inconveniently makes the structure of the voltage measuring apparatus complicated.